Heretofore, as disclosed in Japanese Patent Laid-Open Publication No. 2006-182208, a vehicle interior panel and a molding method thereof have been known as a laminated plate and a manufacturing method thereof. In the molding method, a parison made of a thermoplastic is extruded from an extrusion head, the parison concerned is suspended between one of metal dies and the other metal die, a skin sheet is arranged between the parison and the one metal die, the metal dies are clamped together, and a pressurized fluid is introduced into the parison to perform blow molding for the parison.
However, in such a conventional technology, an inside of the vehicle interior panel is hollow, and there has been a problem that strength of the vehicle interior panel is weak. Accordingly, it is necessary to enhance the strength of the vehicle interior panel by inserting a bridge member into the inside of the vehicle interior panel. However, in the above-described conventional technology, since the bridge member cannot be inserted in advance into the inside of the vehicle interior panel, it is necessary to do work of notching a part of the vehicle interior panel after the vehicle interior panel is molded, inserting the bridge member into the inside of the vehicle interior panel, and thereafter closing such a notched portion again. This work has been cumbersome.
Moreover, in the above-described conventional technology, the vehicle interior panel is molded only by clamping the metal dies together and being blow-molded, and accordingly, a shape cannot be imparted to the vehicle interior panel so that the vehicle interior panel can go along inner surface shapes of the metal dies, and it has been apprehended that distortion may occur on a surface of a panel base material of the vehicle interior panel.
Furthermore, in the above-described conventional technology, an upper portion of the parison is pulled and extended owing to self weight of the parison as the parison is being suspended. Accordingly, there have been problems that upper and lower portions of the panel base material differ from each other in thickness, resulting in a strength difference of the panel among portions thereof, and in an occurrence of the distortion caused by the fact that the vehicle interior panel is cooled after being molded and that a temperature is changed during use of the panel concerned. In particular, as the molded panel is being larger, the upper portion of the parison is significantly thinned. Accordingly, it can be said that such a method of suspending the parison and performing the blow molding for the hollow panel is not very suitable for the molding of a large-size panel.
In this connection, it is an object of the present invention to obtain a laminated plate capable of enhancing strength thereof and capable of suppressing the occurrence of the distortion after the laminated plate is molded regardless of a size thereof, and to obtain a manufacturing method of the laminated plate.